Amphiphilic graft copolymers

ABSTRACT

A novel amphiphilic graft copolymer is described. A process to make amphiphilic graft copolymers via grafting either poly(ethylene oxide) or polylactide side chains onto an EVA platform using oxo-anion ring-opening polymerization chemistry is also described. Polyethylene or polypropylene based graft copolymers are prepared starting from poly(ethylene-co-vinyl acetate) or maleic anhydride grafted isotactic polypropylene respectively. The amphiphilic character will result from the incorporation of hydrophilic poly(ethylene oxide) (PEO) side-chains. Various applications of the novel amphiphilic graft copolymer are also described including, but not limited to, thermoplastic elastomer, films, fibers, fabrics, gels, breathable packaging materials, additive for biodegradable system, surfactant, antistatic additives, polymer compatibilizers, phase transfer catalysts, solid polymer electrolytes, biocompatible polymers, or incorporation into the materials listed above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/834,638, now allowed, filed Aug. 25, 2015, which is divisional ofU.S. patent application Ser. No. 13/973,283, filed Aug. 22, 2013, nowU.S. Pat. No. 9,150,647, which claims priority under 35 U.S.C. § 119(e)to U.S. Provisional Appln. No. 61/691,964, filed Aug. 22, 2012, thedisclosures of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

An aspect of the present invention relates generally to novelamphiphilic graft copolymers. Specifically, polyethylene orpolypropylene based graft copolymers are disclosed as being preparedfrom poly(ethylene-co-vinyl acetate) or maleic anhydride graftedisotactic polypropylene, respectively. Also described is a process tomake amphiphilic graft copolymers via grafting either poly(ethyleneoxide) or polylactide side chains onto an ethylene vinyl acetateplatform or maleic anhydride grafted polypropylene platform usingoxo-anion ring-opening polymerization chemistry. Various applications ofthe novel amphiphilic graft copolymers are also described including, butnot limited to, thermoplastic elastomer, films, fibers, fabrics, gels,breathable packaging materials, additive for biodegradable systems,surfactant, antistatic additives, polymer compatibilizers, phasetransfer catalysts, solid polymer electrolytes, biocompatible polymers,and incorporation into the materials listed above.

BACKGROUND

Ethylene vinyl acetate (EVA) copolymers are commodity materials withweight percentages of vinyl acetate that usually varies from 2 to 40%.EVA copolymers are comparable to elastomeric materials in softness andflexibility, yet EVA copolymers can be processed like otherthermoplastics. EVA copolymers have good clarity and gloss, good barrierand water proof properties, low-temperature toughness, desirable sealantproperties, and resistance to UV radiation. They are inherently tough,resilient and more flexible than low density polyethylene over a broadtemperature range, and have excellent environmental stress crackresistance.

Polyethylene (PE), Ethylene vinyl acetate (EVA), and polypropylene (PP)are common resins in packaging film and medical device applications. EVAis a common sealant in film packaging and is currently used extensivelyin primary packaging applications, including both film-film andpaper-film applications, as well as components of medical devices.Polypropylene can be used as the structural component of packaging filmsand as components of many medical devices.

Polymer films for medical device and packaging must meet a broad rangeof stringent criteria which include: a) functional requirements of theproduct post-sterilization; b) providing a sterile barrier andstructural support for the product over its lifetime after sterilizationwhen used in primary packaging applications; c) being capable of highfabrication rates with a broad fabrication window; d) being costeffective; and e) meeting increasing demands for environmentalstewardship.

Beyond the United States and European countries, radiation basedsterilization techniques are not readily available and ethylene oxide(EtO) sterilization is the primary mode of sterilization used. Abreathable package is required for EtO sterilization. Additionally,non-breathable film-film packages are currently limited with respect tothe geographical markets they can be used due to limitations of thealtitude the package can experience without potentially incurring openseals. At high altitudes the air within the non-breathable packageexpands and can cause open seals, resulting in loss of sterility of theproduct. Paper top webs are common alternatives used in packaging;however, they usually require an adhesive coating which increases thecost. Moreover, paper is susceptible to tearing and punctures, which canresult in the loss of sterility of the product, and possible productrecalls. Direct seal paper packaging is paper packaging without anadhesive coating. Although direct seal paper packaging is a low costalternative, it is difficult to process on current packaging machinesand can have a narrow seal performance window between weak, open seal orstrong seal which result in fiber tear or tearing of the paper. Both theweak seal and paper tears of direct seal paper packaging compromise thesterility of the product. Breathable non-paper films, such as Tyvek®,can be used but they are substantially more costly than conventionalfilms. PEBAX® is a commercially available polyamide/polymer ethercopolymer which offers breathability and steam sterilizationcapabilities while maintaining a sterile barrier. However, like Tyvek®,PEBAX® is a specialized and expensive material.

An approach to achieving breathability of a polymeric film is theconcept of micro-perforated films, which is utilized in a wide varietyof commercial applications, commonly in food packaging and medical &health applications. The food packaging applications primarily apply tofresh product wrapping to enhance shelf life, but are also used inwrapping things such as fresh breads and other baked goods. Thesemicro-perforated films are tailored to have very selective permeationrates to oxygen, carbon dioxide, and moisture. The controlled moisturevapor transmission rate (MVTR) preserves the moisture of the produce andextends its sellable shelf life. Alternatively, perforated films arealso used in medical and health applications. These films typically havelarger perforations thus resulting in poor physical properties and veryhigh MVTR. These films include applications like breathable sheets fordiapers and feminine hygiene products, wound dressings, exam and surgeryroom paper, etc. These films would not have the proper breathability tomaintain a microbial barrier or the required physical properties forprimary packaging of medical devices.

Other approaches to achieving breathability in packaging film are theuse of rigid fillers, such as talc, and application of apost-fabrication stretching to the film. However, the use of rigidfillers results in a film having poor structural integrity and poreswhich would not maintain a microbial barrier. Moreover, the residualrigid filler would contaminate the medical device within the package.

It is desirable to incorporate functional properties onto known polymersto provide desired traits, such as breathability. However, theincorporation of novel chemistries along the polymer chain backbonecannot readily be achieved using known addition polymerization processesof polyethylene or polypropylene without a complicated secondaryreactive process or via a step-growth process. The secondary chemicalmodification processes are often not 100% effective or chemically pure,resulting in incomplete and undesirable secondary reactions whichdetrimentally alter the ultimate chemical, thermal, and physicalproperties of the final polymer. The chain-growth process, the processby which block copolymers are produced, is a multi-step process which iscomplex, time consuming, and costly. While high levels of molecularhomogeneity, including a relatively narrow dispersity index, can beachieved on a laboratory scale, large scale commercial processes usingknown addition polymerization process of polyethylene produce a mix ofmono- and various multi-block structures and a broad dispersity index.

Thus, there is a need for a process capable of modifying EVA and maleicanhydride grafted isotactic polypropylene copolymers by allowing theincorporation of amphiphilic side chains onto the polymer chain backboneat high levels of molecular homogeneity, including a relatively narrowdispersity index. There is also a need for an improved thermoplasticelastomer or commodity resin that would allow for ethylene oxidesterilization in practical packaging and medical device applications.

SUMMARY

One embodiment of the present invention pertains to an amphiphiliccopolymer of the formula (I):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar value of m is in the range from 2 to 40mole percent; the molar values of n is in the range from 60 to 98 molepercent; and p is in the range of 5 to 500 ethylene oxide units.

Another embodiment of the present invention pertains to an amphiphiliccopolymer of the formula (II):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar percentages of grafted maleic anhydrideunits is in the range from 2 to 10 mole percent; the molar values ofpropylene units is in the range from 98 to 90 mole percent; and p is inthe range of 5 to 500 ethylene oxide units.

Yet another embodiment of the present invention pertains to a processfor preparing amphiphilic polyethylene-based copolymers comprisingobtaining an ethylene vinyl acetate copolymer having between 2-40 weightpercent of vinyl acetate; reacting the ethylene vinyl acetate copolymerwith potassium methoxide to prepare a mixture of polymeric potassiumalkoxide and methyl acetate co-product; performing distillation on the amixture of polymeric potassium alkoxide and methyl acetate co-product toremove the methyl acetate co-product; performing ethylene oxidering-opening polymerization on the polymeric potassium alkoxide;removing aliquots during the ethylene oxide ring-opening polymerizationto allow for systemic variation in degree of polymerization of ethyleneoxide side chains; and collecting an amphiphilic polyethylene basedgraft co-polymer having the structure of formula (I):

wherein the molar value of m is in the range from 2 to 40 mole percent;the molar values of n is in the range from 60 to 98 mole percent; and pis in the range of 5 to 500 ethylene oxide units.

According to one embodiment of the process of the present invention, themolar values of m is in the range from 10 to 40 mole percent. Accordingto another embodiment, the molar values of n is in the range from 60 to90 mole percent for n. According to one embodiment, the molar values ofp is in the range from 5 to 400.

In one or more embodiments, the ethylene vinyl acetate copolymer has amelt index from 0.3 to 500 dg/min.

In one or more embodiments, the ethylene oxide ring-openingpolymerization is performed at a reaction temperature in the range of−20 to 100° C. In a specific embodiment, the ethylene oxide ring-openingpolymerization is performed at a reaction temperature greater than 30°C. In yet another specific embodiment, the ethylene oxide ring-openingpolymerization is performed at a reaction temperature of 60° C.

In one or more embodiments, the ethylene oxide ring-openingpolymerization is performed under alkaline conditions.

In one or more embodiments, the ethylene oxide ring-openingpolymerization is performed using 1,3 propane sultone.

In one or more embodiment, the amphiphilic polyethylene based graftco-polymer has a dispersity index in the range of 2 to 10.

Yet another embodiment of the present invention pertains to a processfor preparing amphiphilic polypropylene-based copolymers comprisingobtaining an maleic anhydride grafted polypropylene wherein the molarpercentages of grafted maleic anhydride units is in the range from 2 and10 mole percent; the molar values of propylene units is in the rangefrom 98 to 90 mole percent; reacting the maleic anhydride graftedpolypropylene with a reducing agent to prepare a iPP-diol copolymer,wherein the diol content is equal to the molar percentage of theoriginally grafted maleic anhydride units:

and subsequently performing ethylene oxide ring-opening polymerizationon the iPP-diol copolymer; and isolating an amphiphilic iPP-g-PEOcopolymer having the structure

wherein R represents the end-groups present in either Ziegler-Natta ormetallocene catalyzed polypropylene including, but not limited to,hydrogen, alkyl, substituted alkyl, vinylic substituted alkyl,hydrocarbyl, substituted hydrocarbyl, or vinylic substituted hydrocarbylgroup; the molar percentages of grafted maleic anhydride units is in therange from 2 to 10 mole percent, the amount of diol after reduction ofthe maleic anhydride is in the range from 2 to 10 mole percent; themolar values of propylene units is in the range from 98 to 90 molepercent; and p is in the range of 5 to 500.

According to one or more embodiment of the process of the presentinvention, the molar percentage values of propylene is in the range from90 to 98 mole percent, the molar values of diol derived from reductionof maleic anhydride is in the range from 10 to 2 mole percent, and themolar values of p is in the range from 5 to 400 mole percent.

According to one or more embodiment of the process of the presentinvention, the ethylene oxide ring-opening polymerization is performedat a reaction temperature in the range of −20 to 100° C. In oneembodiment, the ethylene oxide ring-opening polymerization is performedat a reaction temperature greater than 30° C. In another embodiment, theethylene oxide ring-opening polymerization is performed at a reactiontemperature of 90° C.

According to one or more embodiment of the process of the presentinvention, the ethylene oxide ring-opening polymerization is performedunder alkaline conditions.

According to one embodiment of the process of the present invention, theethylene oxide ring-opening polymerization is performed using 1,3propane sultone.

According to one embodiment of the present invention, the amphiphiliciPP-g-PEO copolymer has a dispersity index in the range of 2 to 8.

Another aspect of the present invention pertains to an additive,compatibilizer, thermoplastic elastomer or breathable top web filmcomprising the amphiphilic copolymer of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a synthetic scheme for the preparation of polyethylenebased graft copolymers using a poly(ethylene-co-vinyl acetate) startingmaterial.

FIG. 2 shows the increase in molecular weight as observed by GPC for thegrafting of ethylene oxide from an ethylene-co-vinyl acetate copolymer.

FIG. 3a shows differential scanning calorimetry scans of EVA graftedwith short ethylene oxide side chains.

FIG. 3b shows differential scanning calorimetry scans of EVA graftedwith long ethylene oxide side chains.

FIG. 4 shows a graphical representation of Thermo Gravimetric Analysisof a graft copolymer.

FIG. 5 shows test results correlating side chain length and clarity upondissolution of grafted polymers in water as a function of temperature.

FIG. 6 shows a synthetic scheme for the preparation ofpolypropylene-graft-poly(ethylene oxide) using a maleic anhydridegrafted polypropylene starting material.

FIG. 7 shows an exemplary scheme of oxo-anion elaboration oncommercially available EVA 360 resins.

FIGS. 8-15 show a graphical representation of storage (G′) and loss (G″)DMA temperature sweep data by frequency of a Ziegler-Natta linear lowdensity polyethylene; a blend of 10% PEO-90% Ziegler-Natta linear lowdensity polyethylene; and a blend of 10% of a grafted copolymer of thepresent invention with 90% Ziegler-Natta linear low densitypolyethylene.

FIG. 16-18 show a graphical representation of the tan delta DMAfrequency sweep data by temperature of samples of of a Ziegler-Nattalinear low density polyethylene; a blend of 10% PEO-90% Ziegler-Nattalinear low density polyethylene; and a blend of 10% of a graftedcopolymer of the present invention with 90% Ziegler-Natta linear lowdensity polyethylene.

FIG. 19 shows permeability results of two sample grafted polymer filmsand a non-grafted film blends.

FIG. 20 shows a graphical representation of the tan delta of samples ofa Ziegler-Natta linear low density polyethylene; a blend of 10% of agrafted copolymer of the present invention with 90% Ziegler-Natta linearlow density polyethylene. before and after soaking.

FIG. 21 shows the contact angles of various samples of grafted andnon-grafted films.

FIG. 22 shows stress strain data to prove material physical propertiesare maintained after grafting process of the present invention.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

In general, the present invention describes a process for the chemicalmodification of commodity polyolefins via a chemical grafting-approachto develop novel amphiphilic copolymers having general structures (I)and (II):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar value of m is in the range from 2 to 40mole percent; the molar value of n is in the range from 60 to 98 molepercent and p is in the range of 5 to 500 ethylene oxide units;and

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar percentages of grafted maleic anhydrideunits is in the range from 2 to 10 mole percent, the amount of diolafter reduction of the maleic anhydride, is in the range from 2 and 10mole percent; the molar values of propylene units is in the range from98 to 90 mole percent and p is in the range of 5 to 500 ethylene oxideunits.

By utilizing the vinyl acetate functionality along the polyethylene (PE)backbone or maleic anhydride functionality along the polypropylenebackbone of a commodity resin to create a grafting side group, a verybroad range of functional chemistries could be ultimately incorporated.The potential applications of these functionalized polymeric systems areequally as broad as discussed in detail below.

One or more embodiments of the present invention describe a process tomake amphiphilic graft copolymers via grafting either poly(ethyleneoxide) or polylactide side chains onto an ethylene vinyl acetate (EVA)platform or maleic anhydride grafted isotactic polypropylene platformusing oxo-anion ring-opening polymerization chemistry. Table 1 shows anexemplary sample of ethylene vinyl acetate (EVA) platforms that may beused in the present invention and the Ziegler-Natta linear low densitypolyethylene used as a comparative and used as a blend component forsamples in this patent. Table 2 shows an exemplary sample of polyvinylalcohol-graft-poly(ethylene oxide) (PVOH-g-PEO) copolymers. Tables 1 and2 is not an exhaustive list of EVA platforms and PVOH-g-PEO) copolymersthat may be used in the present invention, but rather an exemplary listof EVA platforms and PVOH-g-PEO) copolymers that may be used in thepresent invention. Commercially available samples of poly(ethyleneoxide) (PEO) of 5,000 and 200,000 g/mol were used, described herein asPEO 5 kDa and PEO 200 kDA, respectively were also used as blendcomponents for samples in this patent.

TABLE 1 Density MI By Weight (g/cc) (g/10 min) Vinyl Acetate Sample ASTMD792 ASTM D1238 Comonomer content Z. N. LLDPE 0.92 1 EVA 360 0.948 2 25%EVA 460 0.941 2.5 18% EVA 660 0.933 2.5 12% EVA 760 0.93 2 9.30% 

TABLE 2 Average Average Molecular —CH₂—CH₂— EO Units Mass Nomen- WeightIntervals Number in Brush Gain clature (kDa)^(a) (Brush Density)^(b)(n)^(c) (%) PVOH360-g- 112.1 14.0 16 182 PEO1 PVOH360-g- 176.9 14.0 31346 PEO2 PVOH360-g- 320.4 14.0 63 707 PEO5 PVOH360-g- 414.0 14.0 84 943PEO6 PVOH360-g- 476.4 14.0 98 1095 PEO7 PVOH460-g- 148.7 17.4 33 299PEO2 PVOH460-g- 221.9 17.4 55 495 PEO3 PVOH460-g- 245.4 17.4 62 558PEO3.5 PVOH460-g- 281.1 17.4 72 654 PEO4 PVOH460-g- 447.6 17.4 122 1100PEO7 PVOH660-g- 180.6 25.3 51 314 PEO2 PVOH660-g- 283.4 25.3 89 550PEO3.5 PVOH660-g- 994.6 25.3 352 2181 PEO14 PVOH760-g- 82.0 35.7 9 39PEO0.25 PVOH760-g- 153.3 35.7 36 160 PEO1.02 PVOH760-g- 157.9 35.7 38168 PEO1.07 PVOH760-g- 395.8 35.7 130 572 PEO3.64 PVOH760-g- 433.8 35.7145 636 PEO4.05 PVOH760-g- 704.9 35.7 249 1097 PEO6.98 ^(a)M_(n) =M_(nPVOH)*(1 + n*44/28) ^(b)D = (M_(nPVOH)/[OH])/28 ^(c)n =([EO]/[E])/(28*[OH])

As with regards to the nomenclature of the grafted copolymers describedherein, eg. PVOH360-g-PEO7, the nomenclature to describe the graftcopolymers prepared is PVOH-###-PEO*, where ### is in reference to thestarting ethylene vinyl alcohol polymer, i.e. 360 refers to EVA 360. Theinteger number * is the ratio of ethylene oxide graft units, value pfrom FIG. 1, divided by the average number of ethylene units in thepolymer backbone, value n from FIG. 1.

Polyethylene Based Materials

EVA's are commodity olefin-based polymers widely used in medical devicesand readily commercially available in a broad range of percentage ofvinyl acetate and molecular weights. Ethylene vinyl acetate (EVA)copolymers have weight percentages of vinyl acetate that usually variesfrom 2 to 40%. EVA copolymers approach elastomeric materials in softnessand flexibility, yet can be processed like other thermoplastics.Ethylene vinyl acetate (EVA) copolymers have good clarity and gloss,barrier properties, low-temperature toughness, stress-crack resistance,hot-melt adhesive, water proof properties, and resistance to UVradiation.

In one or more embodiments, the process of the present inventionutilizes commercially produced ethylene vinyl acetate (EVA) as astarting material. These are olefinic polymers comprised of apolyethylene backbone with vinyl acetate groups along the backbone.Through modification of the vinyl acetate (VA) group, apolyethylene-based system is produced with side groups along thebackbone of tailored chemical functionality. By utilizing the existingvinyl acetate side chain of a commercially produced ethylene vinylacetate copolymer, the modification points are fixed during the EVAsynthesis process and the polyethylene backbone is not altered duringthe chemical modification process. The starting EVA for the presentinvention is preferably prepared by a high pressure free radicalcopolymerization of ethylene and vinyl acetate, with the end-groups ofthe starting material and resultant grafted copolymer being dictated bythe radical initiator employed and the reactions conditions under whichthe copolymerization was performed. A suitable commercially availablepolymer may be chosen as the starting point since the necessaryfunctional group, a hydroxyl group, has already been incorporated ontothe polylolefin backbone as a consequence of the polymerizationchemistry. Various commercially available hydrolyzed EVAc polymer,ethylene vinyl alcohols, and EVAc sources may be used as a suitablestarting material/substrate to prepare the graft copolymers of thepresent invention, including but not limited to, i.e. Elvax® resins(DuPont™), Elevate® (Westlake Chemical™), and Ultrathene® (LyondellBasell™). Because the process of the present invention maintains the PEbackbone of the starting material, the end-groups of the resultant graftcopolymer will governed by the starting EVA starting material. As willother basic materials properties, for example, the length of ethyleneunits present in the EVA copolymer are not changed during grafting frompolymerization and therefore the backbone melting point will only beslightly altered. The number of modification sites would be dependent onthe percentage of vinyl acetate incorporated along the polyethylenebackbone of the starting material. Through the modification of the VAside chains, the process of the present invention can be used to producea polyethylene (PE) copolymer with highly tailorable functionality.Unlike other modification processes known in the art, the process of thepresent invention maintains the PE backbone and does not detrimentallyimpact the dispersity of the PE, or result in undesirable side orsecondary reactions. Maintenance of a narrow dispersity index (PDI) isan indication that cross-linking and/or chain scission did not occur.The present invention maintains a narrow molecular weight distributionfor the grafted side arm. The desired dispersity index of resultantgrafted copolymers of the present invention is preferably in the rangeof 1.05 to 1.25.

In one embodiment of the present invention, polyethylene based graftcopolymers will be prepared from a poly(ethylene-co-vinyl acetate)starting material as shown in FIG. 1. Controlled ring-openingpolymerization is used to graft polymer side chains of ethylene oxideonto the polyethylene backbone to preparepolyethylene-graft-poly(ethylene oxide) (PE-g-PEO) copolymers havingfunctionalized side groups. Incorporation of hydrophilic poly(ethyleneoxide) (PEO) side-chains onto the polyethylene backbone will result in acopolymer with desired amphiphilic characteristics. The grafting densityof the PEO side chains can be varied by the choice of the composition ofthe starting EVA copolymer. EVA compositions with higher vinyl acetatecontent will give higher grafting frequency along the backbone, with theconsequence being fewer ethylene units between branches and thus afforda means of controlling back bone melting characteristics. The ratio ofhydrophobic to hydrophilic content in the graft copolymers can beindependently adjusted by the extent of ethylene oxide polymerization.In one or more embodiments, copolymers of ethylene and vinyl acetateranging in vinyl acetate content from 9 to 40% and melt indexes from 0.3to 500 dg/min may be used as platform materials. A exemplary startingmaterial may have the following structure:

As shown in FIG. 1, the amphiphilic graft copolymers of the presentinvention are prepared in a two-step synthetic sequence. First, ahydrolysis reaction is performed on the EVA platform whereby the acetateunits are removed to produce ethylene vinyl alcohol copolymers (EVOH)and a methyl acetate co-product. In one embodiment of the presentinvention, the acetate units will be removed by reaction with potassiummethoxide and the co-product methyl acetate will be removed bydistillation. The resultant polymeric potassium alkoxide is then used toinitiate ethylene oxide ring-opening polymerization (ROP). In the secondstep of the process, oxo-anion polymerization is performed on thecopolymers of ethylene and vinyl acetate to produce a broad range ofnovel polyethylene based graft-copolymers.

The content of hydroxyl units and sequence length of the ethylene unitsalong the backbone of the starting material is variable. This sequencelength of the ethylene units along the backbone dictates thecorresponding melting point of the copolymer, as well as, the eventualstrength of the final product. The oxo-anion polymerization step of thepresent invention allows for a well-controlled grafting from approachfor the generation of graft copolymers. The chemical nature of thegrafts can be varied to include side groups including, but not limitedto, poly(ethylene oxide), polylactide, polyglycolide, polycaprolactoneor polyester copolymers. The grafted side-arms can be either crystallineor amorphous, hydrophilic or hydrophobic, and either robust orsusceptible to hydrolysis.

The reaction conditions will be such that the ROP will proceed in aliving manner. The resulting graft copolymers will have a narrowdispersity of side-chain graft lengths and a ratio of weight averagemolecular weight to number average molecular weight from 1.05 to 1.25.Two general reaction schemes can be considered for promoting theoxo-anionic ring-opening polymerization. One general reaction scheme forpromoting the oxo-anionic ring-opening polymerization is the use ofalkoxide salts derived from deprotonation of EVOH copolymers withpotassium, rubidium or cesium as counter ions. A second general reactionscheme for promoting the oxo-anionic ring-opening polymerization is theuse of organo-catalysis directly from the EVOH copolymers. Monomers forthe grafting polymerization can be selected from the range of cyclicmonomer that are known to undergo oxo-anion ring-opening polymerizationincluding, but not limited to, ethylene oxide, oxetane, and cyclicesters including lactides and lactones.

The selection of reaction conditions to perform controlled oxo-anionicring-opening polymerization includes the use of anhydrous solvents andreaction temperature in the range of −20 to 100° C. A reactiontemperature greater than 30° C. is preferred to produce higher reactionrates. Reaction pressures will vary according to reaction compositions.A reaction pressure equal to, or slightly greater than, atmosphericpressure is preferred. A narrow dispersity of side-chain graft lengthsis preferred. Removal of aliquots during ROP will allow for systematicvariation in the degree of polymerization of the ethylene oxide sidechains. Molecular weight and side chain graft density of the resultantpolyethylene-graft-poly(ethylene oxide) (PE-g-PEO) copolymers will be afunction of the starting EVA copolymer, and the degree of polymerizationwill be a direct function of the length of time the ROP is performed.Therefore, the process of the present invention allows for an excellentlevel of control over the values of n, m and p. The selection of therange of molar values of n, m and p can span the range from 2 to 40 molepercent for the m, 60 to 98 mole percent for n, and 5 to 500 ethyleneoxide units for p. The preferred ranges will encompass those values ofn, m and p that are present in readily available EVAc copolymers. Thus,the process of the present invention allows for a broad range of controlover resultant compositions of copolymer.

Solvents to perform controlled oxo-anionic ring-opening polymerizationof the present invention can be selected from a range of polar aproticsolvents or a mixture of such solvents including, but not limited to,tetrahydrofuran, diglyme, toluene, or mixtures thereof.

Compositional analysis of the resultant graft copolymers of the presentinvention may be determined using ¹H and ¹³C NMR spectroscopy, as wellas, molecular weight analysis using gel-permeation chromatography.

As shown in FIG. 2 and Table 3, the increase in molecular weight isobserved by GPC for the grafting of ethylene oxide from anethylene-co-vinyl acetate copolymer. The increase in molecular weight ofthe grafted copolymers is evident from the earlier elution timesobserved by gel permeation chromatography (GPC). Representative data isshown in FIG. 2 and Table 3 for the grafting of ethylene oxide from therandom copolymer of ethylene and vinyl alcohol, that was derived byhydrolysis of the corresponding ethylene (vinyl acetate) randomcopolymers. The molecular weight data presented in Table 3 shows the PDI(polydispersity index or dispersity index) is maintained for thegrafting of ethylene oxide from an ethylene-co-vinyl acetate copolymer,indicating a degradation of the polymer backbone or crosslinking doesnot occur during the grafting reaction process.

Tabulated molecular weight data is provided below in Table 3.

TABLE 3 M_(n) M_(w) Polymer [kDa] [kDa] PDI P(E-co-(VA-graft-EO))₁ 78.2226.2 2.90 P(E-co-VA) 52.0 148.6 2.85

As the degree of polymerization of the ethylene oxide side chainsincreases, the poly(ethylene oxide) (PEO) side chains exceed thecritical molecular weight needed to become semi-crystalline and thus theside-chains will crystallize. By utilizing the VA functionality alongthe PE backbone to create a grafting side group, a very broad range offunctional chemistries could be ultimately incorporated by the processof the present invention. The potential application of thesefunctionalized polymeric systems would be equally as broad.

Thermal analysis by differential scanning calorimetry (DSC) can be usedto determine glass transitions temperature and melting points of theresultant semi-crystalline graft copolymers. Thermal analysis by DSC maybe used to establish the expected dual semi-crystalline character of theresultant copolymers, and thermogravimetric analysis (TGA) may beperformed to provide an indication of the upper limit of temperaturestability of the resultant copolymers.

As shown in FIGS. 3a and 3b , DSC scans highlight the ability of thegrafting process of the present invention to create an amorphous orsemi-crystalline side chain by modification of the molecular weight ofthe side chain. FIG. 3a shows EVA grafted with short ethylene oxide sidechains. FIG. 3b shows EVA grafted with long ethylene oxide side chains.

As shown in FIG. 4 and Table 4, the Thermo Gravimetric Analysis of agraft copolymer (PVOH 660-g-PEO14) to a PEO-900 kDa sample shows thatstability of the graft copolymer is comparable with super high molecularweight commercial homopolymer PEO.

TABLE 4 Graft polymers PVOH660-g-PEO14 PEO-900 kDa Temperature @ 2%Weight loss 320° C. 360° C. Char Residual 2.6% 2.5%

To show controlled adhesion of the grafted films with PE, a sample ofPE-g-PEO, pure PEO and HDPE were melt-pressed to thin films. PE-g-PEOand pure PEO thin films were melt-pressed onto HDPE film at 150° C. Itwas shown that PE-g-PEO can be well adhesive to the HDPE, but pure PEOhas no adhesion to the HDPE at all.

As shown in FIG. 5, the frequency of the PEO along the PVOH backbone andthe side chain length can govern when the polymer dissolves. FIG. 5shows test results correlating side chain length and clarity upondissolution of grafted polymers. As shown in FIG. 5, in instanceswhereby copolymers have the same PVOH backbone, the polymers with alonger brush have a lower clear and cloudy point. As shown in FIG. 5, ininstances whereby copolymers have a similar brush length, the copolymerswith higher brush density have a lower clear and cloudy point. Thus, asshown in FIG. 5, the miscibility point in water can be controlledthrough tailoring the side chain lengths and selection of the baseresins in regards to the frequency of the side chains.

Table 5 shows a summary of the differential scanning calorimetry ofvarious grafted copolymers.

TABLE 5 PEO Tm Tc Heat Flow Sample (° C.) (° C.) (J/g) Crystallinity^(a) PVOH360-g-PEO1 18 57 34 17 PVOH360-g-PEO2 40 54 82 40PVOH360-g-PEO5 52 28 119 58 PVOH360-g-PEO6 54 30 126 61 PVOH360-g-PEO762 39 126 62 PVOH460-g-PEO3 51 25 89 43 PVOH460-g-PEO3.5 53 29 97 47PVOH460-g-PEO7 55 32 135 66 PVOH660-g-PEO2 51 24 94 46 PVOH660-g-PEO3.554 32 113 55 PVOH660-g-PEO14 61 39 157 77 PVOH760-g-PEO0.25 20 −39 ~0 ~0PVOH760-g-PEO1 44 12 42 21 PVOH760-g-PEO4 64 31 125 61 PVOH760-g-PEO7 6631 131 64 ^(a) ΔH_(100% crystalinity) = 205 J/g J. Polym. Sci., Part B:Polym. Phys., 2006, 44, 3042-3052.

As shown in Table 5, the values of Tm, Tc and Crystallinity increase asthe number of repeating unit increase on the brush. The polymerizationdegree of PEO can be established by the Tm of PEO.

Poly(Lactic Acid) (PLA)

In another embodiment of the present invention, the grafted side chainscan comprise poly(lactic acid) (PLA) which produce a resultant copolymerhaving a dual semi-crystalline character. Poly(lactic acid) is abio-compatible polymer that is derived from a renewable resource.Breathability would be achieved by selective hydrolysis of thepolylactide side chains to generate porous membranes.

In one embodiment of the present invention, EVOH is used as a startingplatform for the preparation of novel polyethylene-graft-polylactidecopolymers (PE-g-PLA). The grafting density of the PLA side chains canbe varied by the choice of the composition of the starting EVOHcopolymer, and the ratio of hydrophobic to hydrolysable content can beindependently adjusted by the extent of lactide polymerization. Lactideis derived from renewable resources and PLA is a bio-compatible polymer,thus conferring environmental benefits over conventional petroleumderived polyethylenes. Partial, or complete, hydrolysis of the graftedPLA side chains generates porosity in PE-g-PLA copolymers leading tobreathability of membranes from these compositions with the addedadvantage that the extracted porogen is simply lactic acid.

Polypropylene Based Materials

In another embodiment of the present invention, polypropylene may beused as the polyolefin platform substrate. As shown in FIG. 6, the basicsubstrate will be maleic anhydride grafted polypropylene. Maleicanhydride grafted polypropylene is a commodity material available in arange of compositions.

The selection of preferred maleic anhydride grafted polypropylene willhave molar percentages of grafted maleic anhydride units, andconsequently the amount of diol after reduction of the maleic anhydride,in the range from 2 and 10 mole percent; and molar values of propyleneunits in the range from 98 to and 90 mole percent. The preferred rangeswill encompass those values of grafted maleic anhydride that are presentin readily available commercial maleic anhydride grafted polypropylene.

Yet another embodiment of the present invention pertains to a processfor preparing amphiphilic polypropylene-based copolymers comprisingobtaining an maleic anhydride grafted polypropylene wherein the molarpercentages of grafted maleic anhydride units is in the range from 2 to10 mole percent; the molar values of propylene units is in the rangefrom 98 to 90 mole percent; reacting the maleic anhydride graftedpolypropylene with a reducing agent to prepare a iPP-diol copolymer,wherein the diol content is equal to the molar percentage of theoriginally grafted maleic anhydride units;

performing ethylene oxide ring-opening polymerization on the iPP-diolcopolymer; and isolating an amphiphilic iPP-g-PEO copolymer having thestructure

wherein R represents the end-groups present in either Ziegler-Natta ormetallocene catalysized polypropylene including, but not limited to,hydrogen, alkyl, substituted alkyl, vinylic substituted alkyl,hydrocarbyl, substituted hydrocarbyl, or vinylic substituted hydrocarbylgroup; the molar percentages of grafted maleic anhydride units is in therange from 2 to 10 mole percent, and consequently the amount of diolafter reduction of the maleic anhydride is in the range from 2 to 10mole percent; the molar values of propylene units is in the range from98 to 90 mole percent, and p is in the range from 5 to 500.

According to one or more embodiment of the process of the presentinvention, the molar percentage values of propylene is in the range from90 to 98 mole percent, the molar values of diol derived from reductionof maleic anhydride is in the range from 10 to 2 mole percent, and themolar values of p is in the range from 5 to 400 mole percent.

According to one or more embodiment of the process of the presentinvention, the ethylene oxide ring-opening polymerization is performedat a reaction temperature in the range of −20 to 100° C. In oneembodiment, the ethylene oxide ring-opening polymerization is performedat a reaction temperature greater than 30° C. In another embodiment, theethylene oxide ring-opening polymerization is performed at a reactiontemperature of 90° C.

According to one or more embodiment of the process of the presentinvention, the ethylene oxide ring-opening polymerization is performedunder alkaline conditions.

According to one embodiment of the process of the present invention, theethylene oxide ring-opening polymerization is performed using 1,3propane sultone.

According to one embodiment of the present invention, the amphiphiliciPP-g-PEO copolymer has a dispersity index in the range of 2 to 8.

Controlled oxo-anion ring-opening polymerization of ethylene oxide willyield novel compositions of iPP-g-PEO. The grafting density of the PEOside chains can be varied by the choice of the composition of thestarting iPP-diol copolymer. The ratio of hydrophobic to hydrophiliccontent can be independently adjusted by the extent of ethylene oxidepolymerization. The process of the present invention provides a broadrange of control over sample compositions. Molecular weight and sidechain graft density will be a function of the starting maleic anhydridegrafted polypropylene, and the control over the side-chain length willbe a direct function of the length of time the ROP of ethylene oxide isperformed. Breathable films and membranes can be prepared from thePP-g-PEO copolymers, and blends thereof, by compression molding or filmcasting. Breathable membranes can be prepared from the PP-g-PEOcopolymers.

The PP-g-PEO copolymers could also be used as compatibilizers betweentwo incompatible polymeric systems with one component being PP-based, orhaving an affinity for PP, and the other having an affinity for PEO,enhancing the dispersion of the secondary phase and interaction betweenthe two phases resulting in enhanced physical performance, as well asproviding improved product consistency. The PP-g-PEO copolymers of thepresent invention may also be used as a toughening agent to increase thephysical performance attributes of polypropylene, including impact,tear, or puncture resistance.

Other additives could be likewise be driven to the interface between thepropylene and the secondary phase, such as exfoliated graphene or clayplatelets for enhanced oxygen barrier properties. Oxygen scavengerscould likewise be incorporated. Due to high level of dispersion andpropensity for the additive to move to the blend interface, lower levelsof additives would need to be incorporated for a higher level ofperformance and enhanced efficiency.

Fabrication methods for producing articles from the graft modifiedEVA-based copolymers, PE-g-PLA copolymers, or PP-g-PEO copolymersinclude, but are not limited to, mono-layer or multi-layer films whichare blown, cast, extruded, or extrusion coated. Final products may bemade through injection molding, extrusion, blow molding, including thefabrication of fibers.

Additives that may be added to the graft modified EVA-based copolymersPE-g-PLA copolymers, or PP-g-PEO copolymers, blend or multilayer filmcomprising of the graft modified EVA-based copolymers, include but arenot limited to, organic or inorganic particles such as talc, clay, woodor carbon fibers, oils, and other fillers including other polymericmaterials, reinforcing agents, stabilizers, colorants, and processingaids.

Example 1: EVA Platform

In an exemplary embodiment of the present invention, the process of thepresent invention is used to perform polymer side chain grafting viaoxo-anion elaboration on a model EVA 360 using a controlled ring-openingpolymerization of ethylene oxide to producepolyethylene-graft-poly(polyethyelene oxide) (PE-g-PEO) copolymers underalkaline conditions was performed followed by further elaboration of thein-situ generated EVOH by reaction with 1,3 propane sultone. The processof the present invention also allows for the ability to tailor thelength of the side chain to enable the further enhancement of propertymodification, particularly for the breathability optimization, tie-chainlike toughening enhancement and blend or composite compatibility. Thegrafting density of the PEO side chains can be varied by the choice ofthe composition of the starting EVA copolymer, and the ratio ofhydrophobic to hydrophilic content can be independently adjusted by theextent of ethylene oxide polymerization. The amphiphilic graftcopolymers of the present invention may be used in various applicationsincluding, but not limited to, thermoplastic elastomer, films, fibers,fabrics, gels, breathable packaging materials, additive forbiodegradable systems, surfactant, antistatic additives, polymercompatibilizers, phase transfer catalysts, solid polymer electrolytes,and biocompatible polymers or, incorporation into the materials listedabove.

As shown in FIG. 7, 1 equivalent of EVA 360 was dissolved in toluene at90° C. and a hydrolysis reaction was performed on EVA 360 using 2.5equivalents of potassium methoxide in 5 equivalents of Diglyme solventat 50° C. for a period of one day. The resultant polymeric potassiumalkoxide is then used to initiate ethylene oxide ring-openingpolymerization (ROP). In the second step of the process, oxo-anionpolymerization is performed on (copolymers of ethylene and vinyl acetateto produce a broad range of novel polyethylene based graft-copolymers.

Applications

Polyethylene (PE) is one of the most widely used polymeric materialsglobally. Linear low-density polyethylene (LLDPE) in particular is usedin a broad range of applications, including a component in films forpackaging products and medical devices. These are polymeric materialswhich have been used in the medical device industry for decades and areboth low cost and recyclable. The ability of the present invention toincorporate a grafted functional group along the backbone of aconventional PE would enable further enhancement of the performance andapplications of PE-based materials. Because the fundamental backbone ofthe resultant polymeric resin would still be PE, the resultantchemically modified resin could still be readily recyclable.

Although methods of achieving breathability or porosity of packagingfilm may be found in the prior art, none of the known methods offer thebalance of required physical attributes, microbial barrier, commercialscalability and potential price point of the commodity based resinbreathable top web film as described in the present invention.

In another aspect of the present invention, the amphiphilic graftcopolymer is incorporated into a blend of commodity resins to create abreathable top web film for primary packaging for medical devices thatis capable of withstanding ethylene oxide sterilization. The film couldprovide the physical performance attributes of a polymeric film with thebreathability of paper, while also maintaining microbial barrierproperties. Breathable films address altitude issues experienced withnon-breathable primary packages which can result in open seals due topressure differentiation issues. Thus, breathable films may be used inair freight and in geographical areas with a higher altitude. Breathablefilms and membranes can be prepared from the PVOH-g-PEO copolymers, andblends thereof, by compression molding or film casting.

The PVOH-g-PEO copolymers could also be used as compatibilizers betweentwo incompatible polymeric systems with one component being PE-based, orhaving an affinity for PE, and the other having an affinity for PEO,enhancing the dispersion of the secondary phase and interaction betweenthe two phases resulting in enhanced physical performance, as well asproviding improved product consistency. Other additives could belikewise be driven to the interface between the polyethylene and thesecondary phase.

Two (2) novel PE-grafted polymer films were prepared and tested todetermine whether the PE-grafted films could achieve permeability andmicrobial barrier requirements to enable the potential application as abreathable top web for primary packaging of medical devices.

The two (2) novel PE-grafted polymer films were composed of aZiegler-Natta linear low density PE having a density of 0.92 g/cm3(measured using ASTM D792) and a melt index of 1 g/10 minutes (measuredusing ASTM D1238) as follows:

-   -   Film A: Ziegler-Natta linear low density PE (84%),        PVOH760-g-PEO7 (6%), PEO (10%); and    -   Film B: Ziegler-Natta linear low density PE (70%),        PVOH660-g-PEO14 (5%), PEO (25%).

The two (2) PE-grafted polymer films were tested against a non-graftedfilm (Film C composed of Ziegler-Natta linear low density PE (55%) andPEO (45%).

The films were prepared via melt blending and were performed in atwin-screw blender (eg. Brabender Model R.E.E. 6). The blend was fed ata rotor speed of 20 rpm at 160° C. The film was prepared using a feedingsequence wherein the Ziegler-Natta linear low density PE was fed intothe blender first, followed by the PVOH-g-PEO and finally commercialPEO. The rotor speed was increased to 60 rpm upon the melt of allfeeding materials. The temperature was maintained at 160° C. for 10minutes. Upon completion of batch mixing, the blends were rapidlyquenched in liquid nitrogen to freeze the morphology. To prepare thefilms, the blends were placed between sheets of Kapton films and thenplaced between the heated metal platens of a compression press (Carver,Inc). The thickness of films was controlled with 0.1 mm steel foil at150° C. and 15000 PSI for 2 minutes. The films were quenched in liquidnitrogen once left the hot plates. Porous films were obtained from thepressed blends, followed by PEO extraction with water at roomtemperature for 12 hours.

Upon visual examination, the PE-grafted polymer films were moretransparent and homogenous in comparison to the non-grafted film (Film Ccomposed of Ziegler-Natta linear low density PE (55%) and PEO (45%). Thenon-grafted film (Film C composed of Ziegler-Natta linear low density PE(55%) and PEO (45%) has distinct phases, voids and is not transparentwhich is a strong visual indicator of incompatibility andnon-homogeneity in the non-grafted film. The visual examination of thegrafted films evidences that the addition of the PVOH-g-PEO is acompatibilizer for Ziegler-Natta linear low density PE and PEO.

FIGS. 8-15 show DMA data by frequency. The temperature sweeps shows the10% PVOH-g-PEO/90% Z-N LLDPE blend sample has a more consistent G′(storage) and G″ (loss) modulus over the temperature range of at least(−50 C to 70 C) over a broad frequency range of at least 0.1 Hz to 100Hz. With equivalent or greater moduli over at least the giventemperature range. This G′ and G″ data also shows that the 10%PVOH-g-PEO/90% Z-N LLDPE blend sample has the least softeningcharacteristics at elevated temperatures, >40 C. Note there is aslightly lower loss (G″) modulus for the 10% PVOH-g-PEO/90% Z-N LLDPEblend sample specifically at −10 C compared to the neat Z-N LLDPEsample. This is not taken to be impactful compared to the overall trendof the blend sample as a function of temperature and frequency.

FIG. 16-18 show a graphical representation of the tan delta of samplesof a Ziegler-Natta linear low density polyethylene; a blend of 10%PEO-90% Ziegler-Natta linear low density polyethylene; and a blend of10% of a grafted copolymer of the present invention with 90%Ziegler-Natta linear low density polyethylene. The tan delta curves at10, 30, and 50° C., for the 10% PVOH-g-PEO/90% Z-N LLDPE blend sampleshows the lowest tan delta, especially at the lower frequencies <10 Hz.This shows this material will have improved shape and dimensionalstability over the temperature range for commercial applications, such amedical devices, which could be EtO sterilized and/or stored inuncontrolled environments and used in tropical climates. The lowfrequency, 0.1 Hz, data is suggestive this material will have improvedcreep and compression set resistance over the temperature rangecommercial products could be exposed too. This is an advantaged propertyto maintain functional performance of products comprising of at leastone component comprised of the PVOH-g-PEO polymer over the productlifetime especially if under molded in or assembly stresses.

As shown in FIG. 19, PE-grafted polymer films can be controlled to beboth permeable to allow breathability while at the same time having apercentage of penetration to be less than 0.1% thus providing for amicrobial barrier compared to the non-grafted film of Ziegler-Nattalinear low density PE (55%) and PEO (45%) which is not a microbialbarrier and is fully permeable. A film were composed of pureZiegler-Natta linear low density PE having a density of 0.92 g/cm3 and amelt index of 1 g/10 minutes, while a microbial barrier, would not bepermeable and generally do not allow air penetration as defined in theISO 11607 std.

Controlled oxo-anion ring-opening polymerization of ethylene oxide willyield novel compositions of iPE-g-PEO. The grafting density of the PEOside chains can be varied by the choice of the composition of thestarting iPE-diol copolymer. The ratio of hydrophobic to hydrophiliccontent can be independently adjusted by the extent of ethylene oxidepolymerization. The process of the present invention provides a broadrange of control over sample compositions. Molecular weight and sidechain graft density will be a function of the starting graftedpolyethylene, and the control over the side-chain length will be adirect function of the length of time the ROP of ethylene oxide isperformed. Breathable films and membranes can be prepared from thePE-g-PEO copolymers, and blends thereof, by compression molding or filmcasting. Breathable membranes can be prepared from the PE-g-PEOcopolymers.

The PE-g-PEO copolymers could also be used as compatibilizers betweentwo incompatible polymeric systems with one component being PE-based, orhaving an affinity for PE, and the other having an affinity for PEO,enhancing the dispersion of the secondary phase and interaction betweenthe two phases resulting in enhanced physical performance, as well asproviding improved product consistency. The PE-g-PEO copolymers of thepresent invention may also be used as a toughening agent to increase thephysical performance attributes of polyethylene, including impact, tear,or puncture resistance.

Other additives could be likewise be driven to the interface between thepolyethylene and the secondary phase, such as exfoliated graphene orclay platelets for enhanced oxygen barrier properties. Oxygen scavengerscould likewise be incorporated. Due to high level of dispersion andpropensity for the additive to move to the blend interface, lower levelsof additives would need to be incorporated for a higher level ofperformance and enhanced efficiency.

The top web films comprising of the present invention could provide acost savings in specialized applications where commercially availableproducts such as Tyvek is needed. Additionally, paper is highly subjectto property degradation over time and under challenging environmentalconditions, especially when subjected to Cobalt or E-Beam sterilization.These breathable films would provide a more long-term structurallystable packaging alternative. This film could be used for anyapplication which requires controlled breathability, such a fresh foodpackaging applications.

The graft modified EVA-based copolymers of the present invention couldalso be used as a breathable flow wrap packaging material. The cost andperformance of currently available flow wrap with a breathable feature,such as a paper strip, is expensive, difficult to run and slow tosterilize. The breathable film of the present invention offers acost-effective packaging material having improved mechanical propertiesand anticipated higher ethylene oxide permeation rate resulting in asubstantially increased sterilization throughput rate.

A top web film incorporating the amphiphilic graft copolymer of thepresent invention will have structural and sealant properties comparableto existing packaging film structures, while maintaining robust physical& processing properties to meet a broad spectrum of packaging lines andproducts to be used in a variety of environment conditions includingareas of high humidity and temperature.

In another aspect of the present invention, an improved thermoplasticelastomer (TPE) is provided incorporating the amphiphilic copolymers ofthe present invention. The thermoplastic elastomer of the presentinvention may be used for injection molded applications such as medicaldevice components including syringe stoppers, blood collection andclosed-system transfer device membranes, and IV drip chambers. Thethermoplastic elastomer of the present invention may also be used forextrusion applications such as IV tubing, catheter extension set tubingand catheter tubing. Additionally, for stopper applications, there is adesire to move from the conventional thermalset rubbers to an injectionmoldable thermoplastic elastomer which can also be reprocessed,resulting in processing efficiencies, less waste, and potential costsavings.

For syringe stoppers TPE's have been evaluated as a replacement toconventional thermoset rubbers. Due to the melt and crystallizationcharacteristics of TPEs they can be injection molded and reprocessed,where as conventional thermoset rubber stoppers must be cut from sheets,with the unused material being disposed of as scrap. A stopperformulation must achieve the appropriate balance of compression set andelastomeric conformability. For membrane applications, current TPE basedmembranes are challenged to provide a desired balance of goodsealability, high compression set, high wear resistance, and resistanceto coring. For stopper and membrane applications, the thermoplasticelastomer of the present invention may be used in two potentialapproaches to achieve the desired balance of properties. As shown inFIGS. 16-18, this material will have improved creep and compression setresistance over the temperature range commercial products could beexposed as suggested by the low frequency, 0.1 Hz. By controlling thecomposition, frequency, and length of the grafted side chains tomanipulate the crystalline structure as well as the molecularentanglement of the final TPE material and control mobility andsubsequently compression set and creep. A controlled amount ofcross-linking could be imparted post-injection molding to provideadditional strength and avoid undesired properties related to creep anddeformation, such as sticktion. In another embodiment of the presentinvention, the grafting architecture and frequency of polymerizationalong the backbone would be tailored to create a semi-crystallinebackbone with an amorphous or semi-crystalline grafted side chain on theresultant graft copolymer to achieve the desired balance of propertiesfor the stopper or membrane applications. In one or more embodiments, itis desired to have PEO side chains long enough to also crystallize tocreate a more complex crystalline structure. Thus, by controlling thecomposition, frequency, and length of the grafted side chains tomanipulate the crystalline structure, as well as, the molecularentanglement of the final TPE material, allows for control of themobility and subsequently compression set and creep. Together thesemolecular attributes would govern the rheological and physicalproperties of the final product.

For IV tubing, current TPE formulations cannot yet meet the desiredperformance attributes of plasticized PVC. Plasticized PVC is desiredfor its low set, high kink resistance, deformation recoverability,clarity, and tactile feel. An additional challenge with non-polar TPEsis the bonding of the IV tubing to connectors and other fixtures. Theseconnections are typically done via solvent bonding.

Catheter tubing may lose some of its strength in regions of elevatedtemperature and humidity, thus causing difficulty in catheter stick,threading, advancing, and other catheter related complications.Non-ideal pre-insertion softening characteristics can lead to cathetercomplications such as excessive sticktion during insertion.

Many current TPE formulations use some type of plasticizer in theirformulation and most IV tubing and extension sets are comprised ofplasticized PVC. For environmental reasons, there is a desire to removedi-2-ethyl-hexylphthalate (DEHP) and other phthalate-based plasticizersfrom the PVC formulation, as well as, to eliminate the use of PVCentirely. An improved thermoplastic elastomer (TPE) incorporating theamphiphilic copolymers of the present invention would serve this need.

For IV tubing, one approach to address the current deficiencies ofconventional TPEs would be to utilized the process of the presentinvention to produce a copolymer having grafted side chains to break upthe crystallinity of the PE backbone and avoid the undesirable plasticdeformation which can occur in semi-crystalline TPEs which results in apropensity for kinking and/or permanent set after clamping. A controlledamount of cross-linking could be imparted post-extrusion to the graftedcopolymer of the present invention to provide additional strength. Polarfunctionality and other functional attributes could be also incorporatedon the graft side chain of the copolymers of the present invention toovercome the inherent difficulty of solvent bonding TPE tubing toconnectors and other fixtures.

For the catheter tubing, a climate-stable catheter tubing could beachieved through utilizing the process of the present invention. Asdiscussed above, by controlling the composition, frequency, and lengthof the grafted side chains to manipulate the crystalline structure, aswell as, the molecular entanglement of the final TPE material, allowsfor control of the mobility and subsequently compression set and creep.In one or more embodiments of the present invention, a more thermallystable, hydrophobic component would comprise the matrix of the tubingmaterial along with a secondary phase of a hydrophilic componenttailored to have a softening temperature appropriate to the internalbody temperature. An optimized balance of hydrophobicity,hydrophilicity, and softening temperature of the catheter tubingmaterial could be achieved by incorporating a hydrophilic system alongthe backbone of the hydrophobic PE backbone resulting in a cathetertubing which is stronger pre-insertion, has greater softeningcharacteristics upon insertion into the body, and enabling an overallgreater ability for tailoring of performance attributes. This wouldenable production of a catheter tubing that would be stable in hightemperature and humidity conditions and climates and also reducecatheter related complications. Dynamic Mechanical Anaysis (DMA)experiments were conducted to show the stability of the graftedcopolymers of the present invention. To conduct the DMA experiment, thecopolymer samples were merged in reverse osmosis (RO) water at 40° C.for two hours. The samples were patted dried prior to running the DMAexperiments. DMA was run at 40° C., at a frequency scan from 0.1-63 Hz.As shown in FIG. 20, 90% Ziegler-Natta linear low density PE having adensity of 0.92 g/cm3 (measured using ASTM D792) and a melt index of 1g/10 minutes (measured using ASTM D1238) and 10% PVOH-g-PEO blend sampleshows stability in regards to viscoelastic properties after exposure toextreme moisture conditions (i.e. submerged in water). The tan deltacurves for the 10% PVOH-g-PEO/90% Ziegler-Natta linear low density PEhaving a density of 0.92 g/cm3 and a melt index of 1 g/10 minutes blendsample shows the lowest tan delta, especially at the lower frequencies<10 Hz. The low frequency, 0.1 Hz, data is suggestive this material willhave improved creep and compression set resistance over the temperaturerange commercial products could be exposed too. This is an advantagedproperty to maintain functional performance of products comprising of atleast one component comprised of the PVOH-g-PEO polymer over the productlifetime especially if under molded in or assembly stresses. This isadvantaged for performance stability in commercial applications, such amedical devices, which could be EtO sterilized and/or stored inuncontrolled environments and used in tropical climates.

As discussed, thermal analysis by differential scanning calorimetry(DSC) can be used to determine glass transitions temperature and meltingpoints of the resultant semi-crystalline graft copolymers. Thermalanalysis by DSC may be used to establish the expected dualsemi-crystalline character of the resultant copolymers. As shown inTable 6, DSC scans highlight that the graft polymer may help PEcrystallization in a blend system.

TABLE 6 PEO Heat PE Heat Flow Portion Flow Portion Samples (J/g) (J/g)Z-N LLDPE (51.33%), 57.58 64.51 PVOH760-g-PEO7(3.67%), PEO (45%) Z-NLLDPE (55%), 73.76 53.51 PEO (45%)

As shown in FIG. 21, the surface energy of the blend can be controlledmoving from hydrophilic to hydrophobic, also the high contact angles(hydrophobic) after the PEO extraction support that the PEO was trulyremoved from the system.

To show self-adhesion of the grafted films, two sample batches of filmswere prepared as follows: Sample 1 consisted of a blend of 90% by weightof a Ziegler-Natta linear low density PE having a density of 0.92 g/cm3(measured using ASTM D792) and a melt index of 1 g/10 minutes (measuredusing ASTM D1238) and 10% by weight of PEO 200 kDa. Sample 2 consistedof a blend of 90% by weight of a Ziegler-Natta linear low density PEhaving a density of 0.92 g/cm3 (measured using ASTM D792) and a meltindex of 1 g/10 minutes (measured using ASTM D1238) and 10% by weight ofgrafted PVOH760-g-PEO. Each batch was 40 grams and the blends wereprepared in a Brabender Model R.E.E. blender 60 rpm at 160° C. for 10minutes. It was determined that Sample 2 has some adhesion and tackproperties allowing Sample 2 to stick to itself or stick to a smoothsurface for a while without need for any additional adhesive. Incontrast, Sample 1 and a film of pure Ziegler-Natta linear low densityPE did not show adhesion and tack properties. The sample films show thata small amount of grafted PVOH760-g-PEO (10%) can result in tackinessand self-adhesive surface properties.

Since the fundamental backbone of a TPE system incorporating the graftedcopolymer of the present invention would still be PE, the resultantproduct is capable of being readily recyclable.

Another aspect of the present invention is the use of graft modifiedEVA-based copolymers as an additive for biodegradable polymeric systemssuch as PLA or PCL (poly(caprolactone). As an additive, these graftmodified EVA-based resins would increase the thermal and mechanicalproperties of the biodegradable system thereby providing mechanicalperformance enhancement while still yielding a biodegradable and largelybioderived system.

The incorporation of an EVOH-g-PLA copolymer of the present inventioninto a packaging or medical device serves as a mechanical propertyenhancer by resulting in an increase in the modulus andelongation-to-break resulting in an overall increased toughness,including increased impact, tear, or puncture resistance.

The graft modified EVA-based copolymers of the present invention couldalso be used as compatibilizers between two incompatible polymericsystems with one of the components being PE-based or random ethylenecopolymer PP-based materials. As compatibilizers, the graft copolymersof the present invention would serve to improve the dispersion of thesecondary phase and interaction between the two phases resulting inenhanced physical performance and provide improved product consistency.The graft modified EVA-based copolymers of the present invention mayalso be used as a toughening agent to increase the physical performanceattributes of polyethylene or random ethylene copolymer PP-basedmaterials, including increased impact, tear, or puncture resistance. Thelength of the side chain of the graft modified copolymers could betailored to optimize the toughening enhancement and strength/toughnessbalance characteristics for PE-based films. An optimized balance, andenhancement, of the impact and tear resistance of the films could beachieved. This could also be achieved by incorporation of the graftmodified copolymers into a PE or or random ethylene copolymer PP-basedfilm, or film layer, thus enabling down gauging of the film forpackaging applications allowing for less packaging waste and potentialcost savings.

Other additives could be likewise driven to the interface between thepolyethylene, or random ethylene copolymer PP-based materials, andsecondary phase, such as, but not limited to, exfoliated graphene orclay platelets for enhanced oxygen barrier properties. Oxygen scavengerscould likewise be incorporated. Due to high level of dispersion andpropensity for the additive to move to the blend interface, lower levelsof additives would need to be incorporated for a higher level ofperformance and enhanced efficiency.

The chemistry incorporated onto the functional graft of the PE or PPbackbone could be used for product surface functionalization ormodification including, but not limited to, creating an anti-microbialsurface; creating a surface with greater biocompatibility;anti-inflammatory; biofilm formation suppressant; self-lubricating orhigher-slip surfaces; creating an anti-fouling surface; and adhesivesurfaces.

Other potential applications of the graft copolymers of the presentinvention include, but not limited to, use as surfactants, antistaticadditives, polymer compatibilizers, phase transfer catalysts, solidpolymer electrolytes, and biocompatible polymers.

Grafting agents, such as polybutymethacylate, can be used for additionalfunctionality such as an anti-proliferative, anti-inflammatory, oranti-coagulant. The graft modified EVA-based copolymers could also beused to create a drug or protein eluting coating or product. Drugelution rate may be controlled by the degree of hydrolysis of the EVAstarting material. For these applications, a controlled release of thedrug is desired to reduce both short and long term restenosis. If abioreactive drug is released too quickly into the body at too great of aconcentration, this “bolus” can result in localized inflammation andinhibit the healing process. EVA is currently used in many biomedicalapplications as a drug and/or protein eluting material due to its goodflexibility, thermoplastic nature, stability, and low cost.

The graft modified EVA-based copolymers can also be used in applicationssuch as films, fibers, fabrics, blends and mixtures. The vinyl groups ofthe vinyl acetate may be used to create gels through controlled crosslinking.

FIG. 22 shows stress strain data to prove material physical propertiesare maintained after grafting process of the present invention.

Due to the backbone linking nature of the side chain and the fact thatthe modification process of the present invention does not degrade themolecular weight of the starting material, the grafted materials of thepresent invention will have fewer extractable and leachable compared toconventional blends or other modification techniques. Therefore, thegrafted copolymers of the present invention mitigate unintendedinteractions with infusates or excipients, and the transmission of thosecomponents to the patient thus making the grafted copolymers of thepresent invention ideal for medical device applications. The graftmodified copolymers of the present invention are in compliance withmaterials of concern restrictions as listed in Prop 65 and REACH.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An amphiphilic copolymer of the formula (I):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar value of m is in the range from 2 to 40mole percent; the molar value of n is in the range from 60 to 98 molepercent; and p is in the range from 30 to 500 ethylene oxide units. 2.The amphiphilic copolymer of claim 1, wherein R is hydrogen.
 3. Theamphiphilic copolymer of claim 1, wherein the poly(ethylene oxide)groups are grafted by oxo-anion ring-opening polymerization.
 4. Theamphiphilic copolymer of claim 1 having a number average molecularweight (Mn) in the range about 80 to about 1000 kDa.
 5. The amphiphiliccopolymer of claim 1, wherein p is in the range of 30 to 250 ethyleneoxide units.
 6. An additive comprising the amphiphilic copolymer ofclaim
 1. 7. A compatibilizer comprising the amphiphilic copolymer ofclaim
 1. 8. A thermoplastic elastomer comprising the amphiphiliccopolymer of claim
 1. 9. A top web film comprising the amphiphiliccopolymer of claim
 1. 10. An amphiphilic copolymer of the formula (II):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar percentages of grafted maleic anhydrideunits, m, is in the range from 2 to 10 mole percent; the molar values ofpropylene units, n, is in the range from 98 to 90 mole percent, and p isin the range of 50 to 500 ethylene oxide units.
 11. The amphiphiliccopolymer of claim 10, wherein R is hydrogen.
 12. The amphiphiliccopolymer of claim 10, wherein the poly(ethylene oxide) groups aregrafted by oxo-anion ring-opening polymerization.
 13. The amphiphiliccopolymer of claim 10 having a number average molecular weight (Mn) inthe range about 80 to about 1000 kDa.
 14. The amphiphilic copolymer ofclaim 10, wherein p is in the range of 50 to 250 ethylene oxide units.15. An additive comprising the amphiphilic copolymer of claim
 10. 16. Acompatibilizer comprising the amphiphilic copolymer of claim
 10. 17. Athermoplastic elastomer comprising the amphiphilic copolymer of claim10.
 18. A top web film comprising the amphiphilic copolymer of claim 10.19. A component of a medical device formed from a blend comprising: oneor both of polyethylene and a thermoplastic elastomer (TPE); and anadditive comprising one or both of: a polyethylene-poly(ethylene oxide)amphiphilic graft copolymer (PE-g-PEO) and a polypropylene-poly(ethyleneoxide) amphiphilic graft copolymer (PP-g-PEO); wherein thepolyethylene-poly(ethylene oxide) amphiphilic graft copolymer (PE-g-PEO)is according to Formula (I):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; the molar value of m is in the range from 2 to 40mole percent; the molar value of n is in the range from 60 to 98 molepercent; and p is in the range from 5 to 500 ethylene oxide units; andwherein the polypropylene-poly(ethylene oxide) amphiphilic graftcopolymer (PP-g-PEO) is according to Formula (II):

wherein R is hydrogen, alkyl, substituted alkyl, vinylic substitutedalkyl, hydrocarbyl, substituted hydrocarbyl, or vinylic substitutedhydrocarbyl group; m, the molar percentages of grafted maleic anhydrideunits, is in the range from 2 to 10 mole percent; n, the molar values ofpropylene units, is in the range from 98 to 90 mole percent, and p is inthe range of 5 to 500 ethylene oxide units.
 20. The component of amedical device of claim 19 in the form of a film or a tubing.
 21. Thecomponent of a medical device of claim 20 in the form of the film,comprising the polyethylene.
 22. The component of a medical device ofclaim 21, wherein the additive comprises the PE-g-PEO.
 23. The componentof a medical device of claim 22, wherein the film has a percentpenetration of less than 0.1%.
 24. The component of a medical device ofclaim 20, wherein the additive is present in the blend in an amount ofabout 3-10% by weight.
 25. The component of a medical device of claim24, wherein in Formula (I), p is in the range of 30 to 500 ethyleneoxide units.
 26. The component of a medical device of claim 24, whereinin Formula (II), p is in the range of 50 to 500 ethylene oxide units.